Flora in San Diego

A Horticulture Information article from the Wisconsin Master Gardener website, posted 11 Jan 2019 Flora in San Diego San Diego, located about 120 miles south of Los Angeles and immediately adjacent to the border with Mexico, is renowned for its beaches, parks and mild climate. Most people’s image of San Diego is white beaches, palm trees, lush greenery and fl owers blooming throughout the year. However beautiful this may be, it isn’t really true California fl ora. Most of San Diego’s landscape plantings are composed of exotic vegetation: “Paradise on Earth” and “Garden City” are but two of Many of the plants in San Diego are not native. the many expressions used to describe San Diego’s horticultural beauty to the rest of the world. What makes these complimentary names somewhat ironic, however, is that most of what is assumed to be the city’s “natural” greenery has all been planted by recent generations. Only with the introduction of large amounts of imported water by the 1880s did San Diego’s true natural landscapes – one almost devoid of greenery – blossom. World acclaimed horticulturists like Alfred Robinson and Kate Olivia Sessions would also make San Diego their home and further its gardening fame. Ordinary residents too banded together and founded the San Diego Floral Association with its magazine California Garden – the nation’s oldest continuously published horticultural magazine. “ – From The Journal of San Diego History, The Cultivation of Paradise on Earth, Fall 1988, Volume 34, Number 4 (http://www.sandiegohistory.org/journal/1988/october/gardening/) Like much of southern California, the majority of San Diego County was originally covered with coastal sage scrub in the western portions and chaparral in the eastern portions. Chaparral (from a Mexican word for scrub oak, chaparro, meaning “shorty”), is the most common plant community in San Diego – as typical of the area as pine forests are of the mountains. Chaparral is composed of drought-resistant shrubs and low growing vegetation, generally shorter than 8 feet tall. The environment is very hot and dry in summer and mild in winter; drought and fi res are common. The tough evergreen plants of the chaparral are adapted to these conditions, and most have small or leathery leaves, store water in their leaves or deep roots, go Drought-resistant shrubs and low vegetation dormant in the summer, and of chaparral. take advantage of the slightest rainfall to bloom and produce seeds. Southern California’s coastline, now largely developed, was once covered by coastal sage scrub. It was composed of woody shrubs ranging from one to ten feet, typically California sagebrush, white and black sage, California buckwheat, toyon, and lemonade berry. Like the chaparral plants, coastal sage scrub is both drought and fi re-adapted. Coastal sage scrub. Coastal sage scrub now exists only in fragmented remnant habitats. In addition to the dominant shrubs in both coastal and inland areas, there are many smaller blooming annuals and perennials that are rarely seen unless hiking in natural areas. Native plants beach evening primrose, Camisonia cherianthifolia (L), coast monkey fl ower, Diplacus puniceus (formerly Mimulus aurantiacus) (LC), yellow mariposa lily, Calochortus weedii (C), wishbone bush, Mirabilis laevis var. crassifolia (RC), and matilija poppy, Romneya coulteri (R). One of the best places to see native plants in San Diego is at Mission Trails Regional Park, but there are also many other public and private tracts of land in the county that have native chaparral. The native chaparral vegetation has been preserved in offi cial nature preserves such as Los Peñasquitos Canyon Preserve and in other canyons including Switzer Canyon, Tecolote Canyon Natural Park, and Marian Bear Memorial Park in San Clemente Canyon that have escaped development because of the steep topography. Docents of the San Diego Natural History Museum lead walks in Florida Canyon (across from the Zoo parking lot) at certain times. The 2000-acre Torrey Pines State Natural Reserve is an wilderness island in an urban sea, with lots of chaparral as well as the elegant Torrey pine (Pinus torreyana torreyana), the rarest pine in the United States (it only occurs naturally near Del Mar Blooming California lilac, and on Santa Rosa, the second largest of Ceanothus sp. the Channel Islands off the coast of Santa Barbara). Hikers can follow 8 miles of trails through stands of wind-sculpted pines and other plant communities including coastal strand, coastal scrub, salt marsh, fresh Native lemonade berry, Rhus water marsh and riparian on this reserve featuring high broken cliffs and integrifolia, in fl ower. deep ravines on headlands overlooking the ocean. Cabrillo National Monument, at the tip of Point Loma, has native coastal sage scrub habitat along the Bayside Trail and many labeled specimens in the beds around the visitor center. (The superb view of San Diego’s harbor and downtown skyline framed by the Cuyamaca mountains, the Old Point Loma Lighthouse, and in the winter, migrating gray whales, are other reasons to visit). Torrey pines, PInus torreyana torreyana (L), coastal scrub at Cabrillo National Monument (LC, RC) and looking across the bay at downtown San Diego from the Monument Visitor Center. Mission Trails Regional Park encompasses 7,220 acres of both natural and developed recreational areas. About 5,800 acres of rugged hills, valleys and open areas show what the area looked like before the arrival of the Spanish. Most of San Diego County was once covered with chaparral (from a Mexican word for scrub oak, chaparro, meaning “shorty”), the most common plant community in this area. Chaparral is composed of shrubs and low growing vegetation, generally shorter than 8 feet tall. The environment is very hot and dry in summer and mild in winter; drought and fi res are common. The tough evergreen plants of the chaparral are Native chaparral at Mission Trails Regional Park. adapted to these conditions, and most have small or leathery leaves, store water in their leaves or deep roots, go dormant in the summer, and take advantage of the slightest rainfall to bloom and produce seeds. In addition to the chaparral, there are also woodland, coastal sage, and riparian habitats and plant communities of California native plants. Started in 1974, Mission Trails Regional Park has become one of the largest urban parks in the United States. The Visitor and Interpretive Center includes a number of exhibits, a library, a 93-seat theater, and an art gallery. There are many trails in the park, including the Oak Grove Trail leads from the Visitor Center to a small oak woodland with majestic coast live oaks and rare Engelmann oaks and the Visitor Center Loop Trail that goes through coastal sage scrub, chaparral, and riparian woodland habitats. The most popular trail of the park is the Cowles Mountain trail, which goes to the summit for a 360-degree panorama of San Diego County. Another popular stop is the Old Mission Dam, which was built to supply irrigation water to farm land that Yucca schidigera in bloom. supplied food for the Mission San Diego de Alcala. Native plants bush sunfl ower, Encelia californica (L) and chaparral broom, Baccharis sarothroides (LC), the San Diego River along Oak Canyon Trail (RC) and Old Mission Dam (R) at Mission Trails Regional Park. However, most people aren’t that impressed with the grey-green vegetation on the hillsides. The San Diego area has a very mild, Mediterranean-type climate characterized by hot, dry summers and mild, wet winters. The area receives an average of only 10” of rainfall annually right along the coast, 12-15” in the interior valleys and foothills, and up to 40” in the mountains. Early residents quickly realized they could easily grow more showy plants from similar climates throughout the world, and introduced many of the trees, shrubs, and fl owers that people often associate with southern California. Various types of palms came from around the world to join the few native species. From South Africa came the orange- fl owered bird-of-paradise (Strelitzia reginae), various types of succulent ice plants (several genera in the Aizoaceae family, formerly the Mesembryanthemaceae) commonly used as ground covers, African daisy (Arctotis and others), jade plant and aloes that fl ower in the winter. Ornamental plants introduced from Africa include bird of paradise, Strelitzia reginae (L), ice plant, Lampranthus sp. or hybrid (LC), ‘Sticks on Fire’ milkbush, Euphorbia tirucalli (C), red African daisy (RC) and blooming aloe (R). Tall, spire-like Italian cypress (Cupressus sempervirens), rosemary, and olives were imported from southern Europe around the Mediterranean Sea, as well as echiums and aeoniums from North Africa near the Mediterranean, while oleander came from the Middle East. Some of the many plants introduced from southern Europe include Italian cypress (L), olives (LC), and oleander (C). Echiums (RC) and aeoniums (R) came from the Canary Islands and North Africa. Eucalyptus trees and bottlebrush (Callistemon) were brought from Australia, while New Zealand fl ax (Phormium) and New Zealand tea tree (Leptospermum scoparium) came from that island country. Bottlebrush (L) and various species of eucalyptus (LC, RC) were brought from Australia, while New Zealand fl ax (R) comes from that country. From other sub-tropical areas came such common plants such as Brazilian pepper tree (Schinus terebinthifolia and “California” pepper tree (S. molle, really native to Peru) – both now considered invasive species, bougainvillea and the lavender-fl owered Jacaranda tree from Brazil; pampas grass (Cortaderia selloana) and lantana from other parts of South America. California pepper (L) really is native to Peru; bougainvillea (LC) and jacaranda (RC) are from Brazil, and pampas grass (R) comes from southern South America. Hibiscus, camellias, and heavenly bamboo (Nandina) are from China; sago palm (really a cycad, Cycas revoluta) is from south Japan to Java; Ornamental plants introduced from China and other parts of Asia include Chinese hibiscus (L), camellias (LC), heavenly bamboo (RC) and sago palm (R).

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